I need the small frame for the top tube length. Then I need a ridiculous stem to get the bars high enough (and quite a lot of seatpost to get the saddle high enough). This bike puts me in quite a low aggressive position - especially in the drops - certainly not up in the wind admiring the view. I'd probably add another spacer under the stem if the steerer was long enough to fit it (it was a second hand frameset, I didn't get the option of leaving the steerer long).

My other two drop-bar bikes - an On-One Pompino and a Long Haul Trucker - are both 54cm frames, and are both too long in the top tube. I use a 50-60mm stem on each of them to bring the bars closer, up on a big stack of spacers. The three bikes all end up with relatively similar bar position - the LHT is somewhat closer and taller than the DBR, and the Pompino is in between, but all of them are much closer and taller than I can get on a production frame using "normal" parts.

That saddle position on the DBR is universal on all of my bikes. Slammed as far forward as it will go, on a zero-offset post. I think I'd like to go a little further forward still, but I have no way of trying it.

So, my custom frame will have a steep (75°) seat tube angle to bring the saddle forward, short top tube and long head tube to bring the bars up and back. I intend that I should be able to get the same fit position on the new bike as I have on this DBR (and the others), but with the saddle clamped mid-rail, and with a flat ~100mm stem. Like how normal shaped people fit on production frames.

From there, I expect to continue fiddling with my position... but starting from the middle of the adjustment range, rather than hard up against the limits where I am now on all of my bikes. I can tweak saddle position forward _or_ backward. I can swap in shorter _or_ longer stems (angled up _or_ down), I can add _or_ remove spacers. A range of adjustability that is unprecedented for me.

Last edited by barefoot on Wed Dec 26, 2012 6:55 am, edited 1 time in total.

Looks like I'm off to a good start... on a bike that I'm don't really have spousal approval on for another 2 years

* WTB Laserdisc Lite hubs. WTB site has them for US$275 R, US$180 F. Velogear.com.au currently has them for A$99 /set. Would be rude not to, I figured. 32 hole... I like lots of spokes, so that's fine by me. Means I can use a lighter rim.* Velocity Aerohead OC. Velocity store has them for US$72.99 each. Upfront Cycles (just out of Adelaide) has 32h purple ones for A$22.95 each if you buy 4. I really like purple, and I'm sure I'll find a use for the other two . Assym rims on disc hubs is a fundamentally good idea... and allows me to use equal length spokes both sides, front and rear! Which brings me to...* DT Comp spokes. Two sets at A$23 /36 from CRC. Apparently that's 17% less than RRP, but it's certainly cheaper than the A$1.50/spoke my LBS used to charge for Comps. Did I mention that I can use 32 equal length spokes on each wheel? Couple of spares... shouldn't need them if I build properly, but whatever.

And that, boys and girls, is a couple of hours wheelbuild time short of a disturbingly light, rather blingy, ridiculously cheap wheelset for this disc brake road bike that I shouldn't be building until my next significant birthday in 2015.

So... moving right along with my proposed disc road build that I'm not doing yet... the fork.

Given that I'm getting a Chitanium custom frame built (to fit my weird body proportions), I'm not locked in to using any particular components... I can adjust the frame to suit whatever I want to build it out of.

Disc road forks are not yet a common thing, but rigid disc MTB forks are. Road forks are typically ~370mm axle-to-crown, CX is about 395mm, MTB forks longer (to fit frames that are designed for suspension).

evilBay is filled with these forks, for $180-200:

I've seen identical shaped forks with Trigon, Token, Picasso, Corratec and Ritchey logos on them. The disc-only version comes in at 460g, and gets surprisingly good reviews for serious MTB use. The only real detraction seems to be for its length; at 415mm they're shorter than a typical MTB fork (but longer than a road or CX fork). For a road/CX bike, there's ample clearance for whatever tyre I'm likely to put on it (short of a full-on 29er knobbie). They also have a more-than-average 48mm rake, which suits me well (I plan on using a fairly slack head angle, so more fork rake is better to keep the trail under control).

I'm finding a hard time thinking of a reason not to grab one of these forks, then design my frame to suit (ie take the "extra" length out of the head tube).

I went with the branding variant as shown, with a subtle "Picasia" logo on the crown rather than garish "Trigon" logos down the fork legs. $180 delivered for a 460g full-carbon disc fork... can't argue too hard against that.

I also recently stumbled across most of a 9-speed Ultegra gruppo, from somebody who upgraded to 10-speed. The brifters are a bit quirky and the derailer has a few battle scars, but they'll transfer from my old bitsa roadie to the new disc roadie and do the job for a while at least, which will help spread the spend out.

So, really, I'm getting close to being only one frame short of a full build. And so, I'm now in serious frame detail design discussion with XACD and Titan Product. I think I'll go with XACD. Quoted US$800 delivered for a custom Ti disc brake CX frame, but they're known to start bumping up the extra charges once you start speccing anything more than the bare bones so it might stretch a bit closer to the $1k I was reckoning on.

Then the only bits I need to source are the brakes and sundries (cables, tape, probably a headset... most of the remainder can transfer from other bikes or the parts pile)... and a decent crankset/BB if I can sneak it under the radar

barefoot wrote:XACD. Quoted US$800 delivered for a custom Ti disc brake CX frame, but they're known to start bumping up the extra charges once you start speccing anything more than the bare bones so it might stretch a bit closer to the $1k I was reckoning on.

...like an extra $135 to put the brake mount on the chainstay We'll have to wait and see what that $135 gets me... waiting on drawings now.

That's the first iteration of a drawing with my geometry. Yes, it's a bit unusual, no it won't fit you

A few things to be changes - the seat stays in particular (I'll have them in 16mm tubing with S-bends instead of straight 19mm please). I'm not entirely convinced by those dropouts, but that seems to be about the best way to put a disc mount on the chainstay, which is where it should be if I want pannier and fender mounts at the rear dropout.

But I've identified a dilemma. Cable routing.

As shown, they've proposed both shift cables go around the left side of the head tube to a plain cable stop (then bare cables under the BB, traditional road bike style). The brake cable goes down under the right side of the down tube, in full-length housing (or hydro line, I guess), and over (?) the BB to the top of the LH chainstay.

But... I would quite like barrel adjusters for my derailers, at the cable stops on the downtube. And the traditionalist in me would rather see a shifter cable on each side. But then, what becomes of the brake cable?

I've had a very brief trawl of google images, and can't find any clear pictures of what others have done (although many seem to be going with internal cable routing, which doesn't interest me). I'll keep looking for clues.

CX bikes tend to have top-tube routed gear cables, which requires a MTB front derailer (top pull) or a pulley to use a road derailer (bottom pull) (and which precludes the use of barrel adjusters anyway). A seatstay mounted disc brake would just have the cable routed along the top tube.

Any ideas?

It's the problem with going for a Chitanium custom frame... you have to decide all the details... and if you get anything wrong, you can't blame the designer

Brake cable anchors down the middle, so I can have barrel adjusters either side.

I'd like to see a picture of how the brake cable squeezes between the bare front shifter cable and the downtube (then over the BB shell to the chainstay anchor). I'll have to have a good look at my bikes in the morning to see how much clearance there is there.

Another viable option:

Looks a little bit odd having the brake cable up there on top of the DT, but it would keep the cross-overs tidy.

Well, the designer is going to have to accept the blame for whatever he got wrong, because he just clicked the trigger button for one of these:(clicky through for big)

Oy vei, what have I done?

I'm promised to find out in about 4 weeks. Merry Christmas to me!

It came to US$1020 in the end - including freight and a Paypal fee add-on, in addition to the $135 dropouts and another $50 for brushed finish instead of sandblast.

Also in transit are $150 worth of BB7s, $180 worth of carbon MTB fork, $45 worth of (superseded) Cane Creek S8 headset, far too much worth of very pimpy cables. In the shed are $200 worth of half-built wheels.

That means I'd still need to find crankset, derailers, shifters, cassette, bars, seatpost, saddle, tyres and bar tape for ~$345 if I was going to slip in under my estimated $2k budget... which would be a serious struggle (especially considering the benchmark $800 105-equipped bikes are all out of stock at the moment)... although I can make do with existing bits for most of that, for a while at least.

I should be able to recoup a reasonable portion of that by offloading the two bikes that this will displace - that is, the remains of my bitsa roadie (once I pinch the parts I need to finish the build) and my Long Haul Trucker (which is a much more serious touring bike than I want or need right now). At least, that's the official story when the Minister for Defence finds out - I guess she'll notice it under the christmas tree

That's not fly-weight, but it's not meant to be. All straight-gauge tubing, and there's a fair bit of material in those dropouts.

I went for, and designed around, the Trigon/Token/generic carbon MTB fork, as seen featured on your local eBay. I got a "Picasia" branded one, because the logos are more subtle. Uncut, it weighs in at 454g.

Edit to add:

I say "designed around" because it's longer than a standard road fork (420mm re: ~370), so I shortened the head tube to suit. That's not a problem for me because my main reason for going custom was to get a long enough head tube. Even with the 50mm fork correction it's still a 148mm head tube - it would have been about 200mm otherwise (which is kind of ridiculous on a 54cm frame with 500mm top tube, but that's just how I'm built). With a standard 100mm ~7° stem, I'll be in about the same position as I am now on my three drop-bar bikes, each with a ridiculous steep stem on a big stack of spacers. Long back, short arms... need the bars up high and short to be able to reach 'em.

It might be a fairly slow build from here... I need to offload at least one bike before I ask for spousal approval to order this one

barefoot wrote:Well, the designer is going to have to accept the blame for whatever he got wrong, because he just clicked the trigger button for one of these:(clicky through for big)

There was always going to be something

I really should have paid a bit more attention to those clearance dimensions around the crankset area. True to the standard disclaimer with XACD... you get what's on the drawing, whether or not that's what you really wanted.

I test fitted my 6750 Ultegra crankset yesterday. The inner ring hits the chainstay. I had a hunch it would, which is why I put them on. There's only a couple of mm in it, but we currently have an interference fit

If the stays weren't bent so much, to get around a hypothetical tyre that I have no intention of actually running, things would be just fine. The cranks themselves have plenty of clearance, it's just the 32T ring.

As a short-term solution, I think I'll build it up with an old square-taper RSX compact crankset I have in the heap, with a long spindle BB to push the chainline out a bit. That will work fine... but old solid-arm cranks and cartridge BBs are heavy bastards of things, and I've somehow turned into a bit of a weight weenie on this build.

For a long term solution... well, the short-term solution is to buy me some thinking time to work out what the long-term solution might be.

It used to be fairly common practice to push a dent in to the chainstay of a steel frame to get better crank or chainring clearance. I'm reluctant to do this, for fairly obvious reasons... and also because the problem area is just where the bridge is welded in, so deforming the shape of the tube there is going to stress the weld. Other options... maybe a triple crank, as is shown on the drawing, which would have a slightly wider chainline? Maybe figuring out some bodge with a Hollowtech 2 MTB BB, which (as far as I can tell) have narrower bearings and spacers, which can be left out to allow for a BB-mounted chain guide or front derailer or a wider BB shell. Maybe it would be possible to swap the spacers around to push the drive-side crank out a fraction (which would make the pedals assymetric... hmmm...).

Or any other suggested solutions from the assembled wisdom we have here.

I spent this afternoon pulling the SLX crankset and BB out of my MTB, measuring, comparing, mixing and matching to see if I can bodge something up with a MTB BB (with/without spacers) and road crank.

Verdict is... no. MTB crankset has long spindle (and longer spline on LH crank), so requires BB outboard faces to be 5mm further apart. The MTB bearings are 1mm narrower (11mm instead of 12mm), but the MTB unit uses 7mm of spacers (or chainguide brackets etc) to get the additional 5mm. The cups have longer threads, and the plastic pipe is shorter to suit. Even without the pipe (which really doesn't have much function), there's not much scope for getting a wider chainline with any road/MTB parts mix.

But, from getting intimate with a few Hollowtech BBs, I reckon I could get away with ~2mm less spline engagement on the LHS crank, which is really the main implication of adding a spacer behind the BB cup. So I'm now on the scrounge for a spare spacer from my MTB buddies (has to be cheaper and easier than getting one mailed over from Belfast!).

I leant a friend my conventional BB tool, so I couldn't pull the old square-taper bits out of the frames they're in to check whether that's going to be a solution (although sourcing a long-spindle BB isn't a big deal if necessary).

Also, the option of denting the chainstay isn't entirely out of the question. The contact point isn't as close to the bridge as I had thought. I reckon the chainstays have ample strength (they're big for the sake of stiffness), so I'm not too worries about that. Just the process of carefully crushing my beautiful new frame...

All part of the adventure. If I wanted to be sure everything would just work, I wouldn't be building up a custom Chitanium bike...

The lock pin on the LHS crank doesn't quite drop in to its hole now, since the spline is 2mm less engaged than it should be. I'll just have to be careful not to accidentally ride without the pinch bolts done up. Edit - On second thoughts, I'll enlarge the hole on the swing-tab thingy so that the pin can reach the hole and lock in properly.

Starting to look a little bit bike-y now:

(finishing off the rear wheel while the Mrs was out last night). A bit wonky with such a tall fork, but... meh, it's for riding, not looking at

tim

Last edited by barefoot on Wed Dec 26, 2012 8:32 am, edited 1 time in total.

One does not simply spring a custom Ti christmas surprise on one's wife, spend a couple of days "supervising" kids while building a bike up in the shed... and then bugger off for a bike ride

Well... not a long one, anyway

I just took it out for a first test after the kids were in bed - a flat-ish 14km twilight blast (with a couple of adjustments stops along the way). Big grins.

Riding up and down the driveway had given me a few concerns.

Even with a slack head angle and lots of fork rake, which should kick the front wheel way out, I still get a fair bit of toe overlap. I guess that's kind of inevitable with such a short cockpit. Plenty of people have lived with a bit of overlap before... it's no problem at anything more than walking pace. Confirmed on the road this evening. What overlap?

A bigger concern was heel strike on the chainstays. They're really quite wide where the dropouts are welded on, and I have a naturally splay-footed stance. I could certainly kick the stays riding the driveway in sandals, but it's hard to know how that's going to work with a normal pedal stroke. I even started pre-emptively looking at options to get my feet further out... pedal spindle length comparisons, considering the option of an XT 48/36 mountain bike crankset to get a bigger Q-factor. Thankfully, that also turned in to a non-concern once I started pedalling freely. I don't kick the stays unless I do it deliberately.

I'm absolutely stoked with the handling. I was trying to achieve a paradox - agile but stable - with a very slack head angle and long rake fork, and with quite short chainstays. It worked. It goes where I point it, it holds a line as solid as a rock, but is still very nimble and chuckable. That nice feeling of being perched on top of the rear wheel, and having the bike manoeuvre directly around your bum.

I deliberately picked some pretty chopped up roads. Handled them beautifully. Could be the carbon fork, could be the Ti frame... but let's not kid ourselves, it's also likely to be the relatively soft 28mm tyres I've got on. Most notably, it just doesn't get bounced off-line, which I put down to the slack steering. Light wheels accelerate nicely.

I'm currently running a 90mm stem angled down. Started out on 10mm of spacers, then stopped and slammed it. Just about right for fast road riding... I might swap in a 100mm stem and see how that goes. Gives me lots of options for raising the bars for gravel roads, relaxed touring... shredding singletrack...

As ridden, my scales call it 9.04kg. Pedals off it's 8.6kg. Swapping in an alternate seatpost with my Brooks B17 attached adds about half a kilo. I don't think adding bar tape will make a big difference